This invention relates to an improved process for the preparation of SBR-rubbers by the emulsion copolymerization of a mixture of styrene and butadiene.
According to U.S. Pat. No. 3,404,111 SBR-rubbers may be obtained by the emulsion copolymerization, at a temperature of about 5.degree. C., of a mixture of styrene and butadiene, in the presence of a redox system containing p-methane hydroperoxide as the initiator and an activator system comprising ferrous sulphate.7 H.sub.2 O, sodium formaldehyde sulphoxylate, and the sodium salt of ethylene diamine tetra acetic acid.
French Pat. No. 1,430,710 also mentions the use of para-menthane hydroperoxide for low-temperature emulsion copolymerization of a mixture of butadiene and styrene.
British Pat. No. 727,637 describes the emulsion copolymerization, at a temperature between 50.degree. and 90.degree. C., of a styrene/acrylonitrile mixture and of acrylonitrile, butadiene, styrene mixtures, using 1-hydroxy-1'-hydroperoxy-dicyclohexyl-peroxide as the initiator.